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A revised system of abbreviated names is proposed for xyloglucan‐derived oligosaccharides. Each (1→4)‐linked β‐d‐glucosyl residue (and the reducing terminal d‐glucose moiety) of the backbone is given a one‐letter code according to its substituents. The name of the oligosaccharide consists of these code letters listed in sequence from non‐reducing to reducing terminus of the backbone.

In ripening fruits of tomato (Lycopersicon esdentum 1. var 83-C-38), the amounts of cellulose and xyloglucan (XC) remained constant during tissue softening, but the relative molecular weight (M,) of XG decreased markedly and the M, of cellulose declined slightly. These changes could have been due to adivities of nonspecific endo-1,4-@-glucanases and/or buffer-soluble XC endotransglycosylase, both of which increased when tissue firmness declined most rapidly. Tomato extracts also reduced the viscosity of XC solutions, especially in the presence of added XC oligosaccharides. This depolymerizing (XCase) capacity differed from 8-glucanase and XC transglycosylase activity (a) by being almost entirely buffer insoluble, and (b) by declining precipitously during fruit softening. Although it disappeared from ripe fruit, XCase may have functioned in promoting wall loosening at earlier stages of fruit development when its activity was highest. By contrast, during aging of fruit in the ripening-inhibited mutant rin there was no change in M, of XC or cellulose, and activities of B-glucanases and XC transglycosylase were lower than in wild-type tomato. Nevertheless, some softening of the fruit did take place over time and XC amounts declined, possibly because high XCase activity was maintained in the mutant, unlike in wild-type fruit.

xylose/galactose/fucose, 4:3:1:1) and a heptasaccharide (glucose/xylose, 4:3), which appeared to be distributed at random, but primarily in alternating sequence. The xyloglucan:cellulose complex was examined by light microscopy using iodine staining, by radioautography after labeling with PHlfucose, by fluorescence microscopy using a fluorescein-lectin (fucose-binding) as probe, and by electron microscopy after shadowing. The techniques all demonstrated that the macromolecule was present in files of cell shapes, referred to here as cell-wall 'ghosts,' in which xyloglucan was localized both on and between the cellulose microfibrils. Since the average chain length of pea xyloglucan was many times the diameter ofcellulose microfibrils, it could introduce cross-links by binding to adjacent fibrils and thereby contribute rigidity to the wall.

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